The present disclosure relates generally to ultrasonic holography imaging systems for use in generating three-dimensional images by acoustic waves, and more particularly, to methods for imaging features within physical items using ultrasonic holography.
In systems for use, for example, in non-destructive testing of physical items, non-invasive techniques are often required in order to determine conditions within an interior of a physical item. Ultrasonic vibrations have the capability of penetrating into and reflecting out of, or passing through, a solid physical item. By analyzing alterations in the patterns and frequencies of the ultrasonic vibrations after they have passed through a physical item, a visual image of the physical item, including features within the physical item, can be generated.
Specifically, an ultrasonic generator causes an emitter element (transducer) to produce a directed sound field that propagates into a physical item to be tested. In some imaging systems, reflections of defects within the physical item, for example, are directed at least in part, back to a receiver. The emitter and receiver elements may be separate components within an array, or may be the same individual component functioning both as an emitter and a receiver (referred to as a “transceiver”); similar to the manner in which a speaker can also function as a microphone. The sound field generates electrical impulses within the receiver. The electrical impulses are converted into data, which is processed to create a visual image. Phased-array transducers are used to provide a series of separate sound impulses (“tone bursts”) that can be separated in time from each other, to enable a directed sound field to be generated. For example, if an array of individual ultrasonic transducers is actuated so that tone bursts are emitted that are spaced apart in time a fixed amount between adjacent emitters, an angled planar sound wave can be generated.
Existing phased-array transducers produce sound fields that have shapes that are derived from by the configuration of the transducer array, which is typically planar or a simple curved shape. Furthermore, existing ultrasonic generators produce only shifts in phase between waves emanated from separate emitters. This limits the capacity for existing ultrasonic holography imaging systems to produce complex forms of wave fronts. Accordingly, it would be desirable to provide an ultrasonic holography imaging system that is capable of producing detailed sound fields that are not constrained by the configuration of the transducer array, so as to provide enhanced imaging that is capable of addressing the shape and configuration of the physical item being imaged.